The present invention relates to a device for actuating a hydraulic brake of a vehicle. The present invention, employing a piston instead of a ball, can be used to lock the brake system of a vehicle for anti-theft purposes and for preventing the vehicle from rolling down when parked on a slope.
At the present, anti-theft systems can be roughly divided into two types: alarm systems and hydraulic lock systems. The former employs only an alarm trying to threaten away a would-be thief but, very often, in vain. The latter, co-operating with the hydraulic brake system of the vehicle, can lock the brakes to protect the car from being moved. Therefore, a hydraulic lock system which co-operates with a hydraulic brake system is the most effective anti-theft system.
Conventionally, hydraulic lock systems can be divided into electromagnetic valve-type systems and ball valve-type systems. In the electromagnetic valve type systems, an electromagnetic valve, being electrically connected to a circuit, communicates with a pipe of the hydraulic brake system. Depending on whether a current is directed through the circuit, the valve is closed thus preventing a hydraulic medium from flowing through the pipe so that the brake is locked.
A first problem of the electromagnetic valve-type systems is that the circuit can be easily cut off, thus opening the valve, so that the brake is released. As a result, electromagnetic valve-type anti-theft systems can be easily broken through. A second problem of these systems is that, if the circuit malfunctions while driving, the brakes would be suddenly locked and the vehicle is stopped instantly so that the driver might be badly hurt and the vehicle might be seriously damaged if being hit by a vehicle following. Accordingly, improvements are needed.
In the ball valve-type systems, a ball valve, including a housing formed with a plurality of through holes and a ball therein formed with a plurality of channels, communicates with a pipe of the hydraulic brake system. The ball is rotatable, so that the valve is opened or closed depending on an alignment between the holes and the channels.
A first problem of the ball valve-type systems is that the ball is easily worn out by a friction between the housing and the ball, thus increasing a clearance between the housing and the ball thus the hydraulic medium is apt to leak out of the valve. As a result, the hydraulic brake system does not function properly.